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/**

用纯代码开发的过程

1. 确定界面元素，要有什么内容
2. 用代码来搭建界面
3. 编写代码
*/
@interface HMViewController ()

@property (nonatomic, strong) UILabel *noLabel;
@property (nonatomic, strong) UIImageView *iconImage;
@property (nonatomic, strong) UILabel *descLabel;
@property (nonatomic, strong) UIButton *leftButton;
@property (nonatomic, strong) UIButton *rightButton;

/** 当前显示的照片索引 */
@property (nonatomic, assign) int index;
/** 图片信息的数组 */
@property (nonatomic, strong) NSArray *imageList;

@property (nonatomic, strong) Person *person;
@end

@implementation HMViewController

/**
懒加载(延迟加载)，通过getter实现

效果：让对象在最需要的时候才创建！
*/
- (NSArray *)imageList
{
    NSLog(@"读取图像信息");
    if (_imageList == nil) {
        NSString *path = [[NSBundle mainBundle] pathForResource:@"ImageList" ofType:@"plist"];
        _imageList = [NSArray arrayWithContentsOfFile:path];
    }
    return _imageList;
}

#pragma mark - 控件的懒加载
// 在getter方法中，不要再使用self. 否则会重复调用getter方法，造成死循环
- (UILabel *)noLabel
{
    if (_noLabel == nil) {
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 20, self.view.bounds.size.width, 40)];

        _noLabel = label;
        _noLabel.textAlignment = NSTextAlignmentCenter;
        [self.view addSubview:_noLabel];
    }
    return _noLabel;
}

- (UIImageView *)iconImage
{
    if (_iconImage == nil) {
        CGFloat imageW = 200;
        CGFloat imageH = 200;
        CGFloat imageX = (self.view.bounds.size.width - imageW) * 0.5;
        CGFloat imageY = CGRectGetMaxY(self.noLabel.frame) + 20;

        _iconImage = [[UIImageView alloc] initWithFrame:CGRectMake(imageX, imageY, imageW, imageH)];
        [self.view addSubview:_iconImage];
    }
    return _iconImage;
}

- (UILabel *)descLabel
{
    if (_descLabel == nil) {
        CGFloat descY = CGRectGetMaxY(self.iconImage.frame);
        _descLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, descY, self.view.bounds.size.width, 100)];
        _descLabel.textAlignment = NSTextAlignmentCenter;

        // 需要Label具有“足够的高度”，不限制显示的行数
        _descLabel.numberOfLines = 0;
        [self.view addSubview:_descLabel];
    }
    return _descLabel;
}

- (UIButton *)leftButton
{
    if (_leftButton == nil) {
        _leftButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
        CGFloat centerY = self.iconImage.center.y;
        CGFloat centerX = self.iconImage.frame.origin.x * 0.5;
        _leftButton.center = CGPointMake(centerX, centerY);

        [_leftButton setBackgroundImage:[UIImage imageNamed:@"left_normal"] forState:UIControlStateNormal];
        [_leftButton setBackgroundImage:[UIImage imageNamed:@"left_highlighted"] forState:UIControlStateHighlighted];
        [self.view addSubview:_leftButton];

        _leftButton.tag = -1;

        [_leftButton addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];
    }
    return _leftButton;
}

- (UIButton *)rightButton
{
    if (_rightButton == nil) {
        _rightButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
        CGFloat centerY = self.iconImage.center.y;
        CGFloat centerX = self.iconImage.frame.origin.x * 0.5;
        _rightButton.center = CGPointMake(self.view.bounds.size.width - centerX, centerY);

        [_rightButton setBackgroundImage:[UIImage imageNamed:@"right_normal"] forState:UIControlStateNormal];
        [_rightButton setBackgroundImage:[UIImage imageNamed:@"right_highlighted"] forState:UIControlStateHighlighted];
        [self.view addSubview:_rightButton];

        _rightButton.tag = 1;

        [_rightButton addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];
    }
    return _rightButton;
}

/** 在viewDidLoad创建界面 */
- (void)viewDidLoad
{
    [super viewDidLoad];

    // 显示照片信息
    [self showPhotoInfo];
}

/**
重构的目的：让相同的代码只出现一次
*/
- (void)showPhotoInfo
{
    // 设置序号
    self.noLabel.text = [NSString stringWithFormat:@"%d/%d", self.index + 1, 5];

    // 设置图像和描述
    self.iconImage.image = [UIImage imageNamed:self.imageList[self.index][@"name"]];
    self.descLabel.text = self.imageList[self.index][@"desc"];

    self.rightButton.enabled = (self.index != 4);
    self.leftButton.enabled = (self.index != 0);
}

// 在OC中，很多方法的第一个参数，都是触发该方法的对象！
- (void)clickButton:(UIButton *)button
{
    // 根据按钮调整当前显示图片的索引?
    self.index += button.tag;

    [self showPhotoInfo];
}

注意：

1) 问题分析：每一次调用showPhotoInfo方法都会实例化一次数组
解决办法：将数组实例化方法移动至viewDidLoad方法
2) 问题分析：

1) viewDidLoad方法过于冗长
2) 控件计算位置时，彼此依赖
解决办法：
利用控件的getter方法，实现控件的懒加载

3) 问题分析：图片信息与代码的耦合性还是太强
解决办法：采用plist的方式定义图片信息内容
提示：这是从网络加载数据的前奏，在程序开发过程中，应该尽量让数据内容与程序代码分离！

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